Neutron generators (NGs) or electronic neutron generators (ENGs) are widely applied in fast neutron-induced gamma-ray spectroscopy for the elemental characterization and inspection of materials, such as, for example, explosives and contraband, in the oilfield, coal, and cement industries, heavy mechanical production, radiography, nuclear security applications, art conservancy, detective work, and medicine. There is a need to monitor the yield of neutron generators in order to determine the performance of the generators. For example, since the neutrons are produced electrically, the outputs of the neutron generators may fluctuate. In such a situation, it may be desirable to monitor neutron outputs during any experimental run to normalize the gamma-ray spectra.
One method of detecting neutrons is based on their elastic scattering of incident neutrons on hydrogen-containing scintillators. This results in a recoil proton ranging in energy up to the neutron's full energy. The energy of the recoil protons is deposited in the scintillator and converted to light. Among the large variety of hydrogen-containing scintillators available, liquid scintillators and plastic scintillators are inexpensive, and therefore most often used. Although such scintillators efficiently detect neutrons, they also are sensitive to gamma rays that usually accompany the neutrons. Hence, to accurately determine the fast neutron output of the neutron generators, it is necessary to distinguish the contribution of gamma-rays from the neutron counts in the neutron detector's total response.
Another method involves the use of a foil of a pure element, such as copper, as an activation target. The foil is exposed to the neutron generators for a selected period of time during which the neutrons from the neutron generators cause nuclear transformation in atoms in the foil, producing new, short-lived, radioactive atoms. A radiation detector is then used to measure the decay of these atoms, and thus to infer the incident neutron flux to which the foil was exposed.
However, there appears to be few or no instruments that are commercially available, which are capable a monitoring the yields of neutron generators or other particle emitting generators. As a result, producers and users of neutron generators or other particle-emitting generators may be required to develop their own, ad-hoc approaches for measuring particle yields. Further, such individual solutions are generally not well documented or standardized and, as a result, it is often difficult or impossible to confidently compare yield measurements made by different producers or users.